Parent Keyword Validation

The Parent keyword validation ensures that Profile definitions reference valid base resources or profiles according to the FHIR Shorthand specification.

Implementation

Components

FHIR Resource Registry - Comprehensive lists of FHIR R4 and R5 base resources (~150 each)
- Canonical URL validation
- External IG profile detection (USCore, mCODE, etc.)
Profile Validation - Enhanced validation logic with appropriate severity levels
- Multi-tier validation logic
- Support for profile-to-profile inheritance

Validation Logic

The validation follows a layered approach:

1. Is it a FHIR base resource? (Patient, Observation, etc.)
   → ✅ Valid

2. Is it defined locally in the symbol table or resources list?
   → ✅ Valid

3. Is it a valid canonical URL?
   → ✅ Valid (if format is correct)
   → ❌ Error (if format is invalid)

4. Does it match a known external IG pattern? (USCore*, mcode-*)
   → ⚠️ Warning (cannot verify locally)

5. Otherwise
   → ⚠️ Warning (unknown, might be typo)

Supported Parent Formats

1. FHIR Base Resources

Profile: MyPatientProfile
Parent: Patient

2. Locally-Defined Profiles

Profile: BaseProfile
Parent: Patient

Profile: DerivedProfile
Parent: BaseProfile  // References profile defined above

3. Canonical URLs

Profile: CustomProfile
Parent: http://hl7.org/fhir/us/core/StructureDefinition/us-core-patient

4. External IG Profiles

Profile: ExtendedUSCore
Parent: USCorePatientProfile  // Warning: cannot verify locally

Diagnostic Messages

Valid Cases (No Diagnostic)

Parent is a FHIR R4/R5 base resource
Parent is a locally-defined profile (by name or ID)
Parent is a valid canonical URL

Warnings

Unknown Profile: Not a FHIR resource, local profile, or recognized external IG

Parent 'UnknownResourceType' is not a known FHIR resource, locally-defined profile, or recognized external profile
Help: Verify the spelling, ensure the parent profile is defined, or use a canonical URL

External IG Profile: Appears to be from a known external implementation guide

Parent 'USCorePatientProfile' appears to be from an external implementation guide and cannot be verified locally
Help: Consider using the canonical URL instead, or ensure this profile is defined in your dependencies

Errors

Missing Parent: Profile lacks required Parent keyword
```
Profile 'MyProfile' must specify a Parent
```

Invalid URL: Canonical URL format is incorrect

Invalid canonical URL format: URL is too short to be valid
Help: Ensure the URL follows the pattern: http(s)://domain/StructureDefinition/profile-id

Known External IG Prefixes

The validator recognizes these common implementation guide patterns:

USCore* - US Core profiles
mcode-* - mCODE (Minimal Common Oncology Data Elements)
QICore* - Quality Improvement Core
CARIN* - CARIN Alliance profiles
DaVinci* - Da Vinci Project profiles
PACIO* - PACIO Project profiles
IPA* - International Patient Access
IHE* - Integrating the Healthcare Enterprise
AU*, UK*, CA*, CH* - Regional profiles (Australia, UK, Canada, Switzerland)

FHIR Version Support

The registry supports both FHIR R4 and R5:

R4: ~145 base resources
R5: All R4 resources plus ~30 new resources (e.g., Transport, Permission, SubscriptionTopic)

Version detection: Currently defaults to R4, with R5 support available via check_profile_assignments_with_version().

Testing

Run validation on test examples:

fsh-lint lint examples/test-parent-validation.fsh

Future Enhancements

Potential Improvements

FHIR Version Detection: Auto-detect FHIR version from project configuration
External Profile Cache: Download and cache external IG definitions for verification
Configuration Support: Allow users to specify known external profiles in .fshlintrc
Canonical URL Resolution: Resolve and verify canonical URLs against known registries
Symbol Table Enhancement: Index profiles by both name and ID for faster lookup

Configuration Example (Future)

{
  "validation": {
    "fhirVersion": "R4",
    "knownProfiles": [
      "USCorePatientProfile",
      "USCoreCondition"
    ],
    "externalIGPaths": [
      "./node_modules/fhir-us-core"
    ]
  }
}